This invention relates generally to circuit breakers, and more particularly to a compressed-gas insulated circuit breaker having a compact drive mechanism for positioning a movable contact within the circuit breaker.
The power demands of our country have reached such proportions that it is now necessary to transmit power to cities at voltages of 115,000 volts and upwards. Present practice is to use a cable system under the city streets with risers to outdoor substations and switch yards. The switch yards comprise the disconnect switches, circuit breakers, lightning arresters, transformers and auxiliary apparatus, so connected as to provide electrical service to local areas. With prior substation construction techniques, the area required for a typical, say 345 KV. substation, is indeed large. For such a substation, the total land requirements could approach 17 acres. Such large parcels of land may not be available at the desired locations.
One recent method utilized to reduce the space requirements for substations is the use of gas-insulated substations. In these gas-insulated substations, all electrical conductors are enclosed in grounded conducting pipes containing a pressurized high dielectric insulating medium such as sulfur-hexafluoride gas. The disconnect switches, circuit breakers and other components are included in the pressurized gas system, and are located above as well as alongside the power transformer to permit short bus runs and minimize space requirements. A typical gas-insulated substation can reduce the area and volume requirements to about 1/20 the requirement of a conventional, similarly sized station.
In addition to reducing the space requirements, the gas-insulated substations have additional advantages. The substations have lower installation and site preparation cost, mainly because of the lowered land acquisition costs, and the fact that the compressed-gas insulated systems have more compact pieces which can be factory assembled, thereby minimizing installation costs. Also, the gas insulated substations have superior reliability, less maintenance costs, and greater personnel safety, since the metal enclosures are grounded and operating personnel are protected from contact with electrically live parts. A further advantage of gas insulated substations is their environmental acceptability and adaptability. All components are enclosed in sulfur-hexafluoride gas, which provides for a quieter operation, and an operation which does not emit light, heat, gas, or arc combustion products to the atmosphere. Also, the gas-insulated substations are adaptable; they can easily be worked into the local environment and can be built inside a building or behind a architectural screen wall, or, if so desired, other structures can be built over them for multiple uses of available land.
In order to achieve the desired space reductions, all substations components should be designed to be as compact as possible. This requires not only that the active components be as closely spaced together as possible, but that their associated equipment, such as drive mechanisms, be as compact as possible and be capable of operating as close to the active components as possible.